Bogie-type suspensions for trucks are comprised of two axles and a central spring pack on each side of the truck chassis, and also equipped with upper and lower reaction rods for the longitudinal linkage of the axles, central hangers with pivoting bearings and supports for housing the reaction rods and the springs in the chassis and on the axles.
Bogie suspensions have the characteristic of having a good load distribution between the axles, being most used for application in 6×4 trucks, on the rear axles, in order to guarantee the tire adherence on the ground.
Although these suspensions are more expensive, compared to spring pack and equalizer models, they are the most used for severe applications in trucks in off-road conditions, due to the need to reduce the time and maintenance frequency, having more vehicle availability to work.
These suspensions are also used for trucks on road applications, due to legal requirements in relation to combinations with trailers and/or semi-trailers, being the suspensions used in these cases very rigid, therefore low comfort for drivers due to vibration.
Among the solutions adopted and known in the state of the art for this type of suspension is the model shown in FIG. 2, which gains prominence due to the position of the pivoting bearing being in lower part of the spring pack. Said suspension also uses axle rebound stop located at the front and rear ends of the suspension with the axles as shown, and springs brackets with removable wear plates with the springs fixed rigidly to each other and to the axle.
These suspensions of the state of the art which have articulating pivot located in the lower part of the spring pack are in general designed in solid and cylindrical bearings mounted on metallic bushing, roller bearings or elastomeric bushing.
The pivot located in the lower part of the spring pack is normally positioned in a region far from and right below the chassis, owing to the space and conditions available by the structural disposition of the vehicle, thus hampering the construction of the anchor frame with the chassis, which supports the articulating bearing of the suspension spring.
The articulating bearings of said suspensions having cylindrical and solid concept, such as revealed in the state of the art, be they with metallic bushing, roller bearings or elastomeric bushing, hamper the process of assembly and disassembly in the vehicle, as they only allow movement and displacement laterally to the chassis. To be disassembled in the case of vehicle maintenance, the wheels must be removed.
Patent document U.S. Pat. No. 6,206,407 illustrates an example of rear bogie-type suspension for trucks, describing a concept of articulation of the suspension between the two axles in the upper part of the spring, which is not exactly a pivot, as it is constructed such that the articulation of the spring occurs by elastic deformation, by an axle-box with various layers of elastomers, interconnected by metal plates.
In the suspension described above, the concept of bearing is idealized in a complex manner, and to be manufactured requires the use of complex and more expensive technologies and processes.
The document cited above also shows a system for fastening the bearing to the chassis by way of fasteners or screws, having the disadvantage of hampering the vehicle assembly process, by requiring an approximation and accurate alignment to coincide with the housing holes in the support.
It must be highlighted that to mount said bearing on the chassis support, it is necessary to use special means and tools, suitable for moving the bearing until it coincides with the housing holes in the support, further worsened by the residual distortion resulting from the elastic memory characteristic which normally results from the manufacturing process thereof, requiring an additional effort from the assembler to correct it, making the assembly process hard and more expensive.
The other matter cited previously is that the bogie suspensions of the state of the art also use axle rebound stop, which are normally conceived by way of steel cables mounted on terminals, which are housed in brackets, bolted to the chassis and to the axles.
The function of said axles rebound stop is to act as safety devices to provide for any failures of the components, which support the axles to avoid the displacement and, to stop of the suspension and axles rebound.
One of the drawbacks of the axles rebound stop cited in the current art is the high cost, because they are made of various and complex components, also due to the various manufacturing processes they undergo, and the installation difficulty, which generates wasted material and labor and, the necessity for more logistic controls.
Another drawback presented in said axles and suspension rebound stop is that since they are comprised of various and complex components, they tend towards failure due to the variability of the manufacturing and installation processes, thus being subject to functional problems, which may cause damage to the suspension, to the vehicle, and offer risk of accidents with other vehicles on the road, and to their users.
Document U.S. Pat. No. 5,078,420 refers to tandem axle suspension characterized by the fact that it has means for interconnecting each end of the springs to the axles, which comprises a spring anchoring mounted on the lower part of the end of the springs and a bracket on the axle mounted thereon, which extends upwards involving an elastomeric shock absorber, with the aim of eliminating the upper torque rods, and allow the joint axes relative to the springs pack in transversal and longitudinal direction.
The drawback of the system described is that it is comprised by various and complex components and, which consequently increase costs and also propensity to failures.
Among the drawbacks found in the rear bogie-type suspensions for the state of the art trucks, the most relevant is the constructive difficulty of the anchoring of the pivoting bearing, owing to the fact that it is positioned beneath the spring pack and far from the chassis, which requires a construction of a more complex frame, with greater consumption of material and more manufacturing processes, resulting in considerably higher weight and costs.
Another drawback presented in the rear bogie-type suspensions used today in trucks is the difficulty in assembling the kit of springs and bearing on the support and the chassis, causing wastage and lost time with more stages in the assembly line and the necessity for specific devices.
There is therefore a need in the state of the art to provide a new rear bogie-type suspension to solve the drawbacks cited, more specifically in simplifying and improving the system of pivoting bearing and its anchor pin fastened to the central hanger, in a more robust manner, and also to provide a safer axle rebound stop, whereby reducing the possibility of suspension failure.
These new constructive forms will also contribute to improve the assembly conditions and comfort of the suspension on the vehicle, as it also allows the use of a two pieces bearing, plus the possibility of vertical mounting of the spring pack on the vehicle, and also the use of an elastomeric cushion at the ends of the leaf spring.